The invention relates to a method for operating a controller which is connected to a bus, in particular a CAN bus. It also relates to such a controller. CAN stands for “Controller Area Network”. The CAN bus is an asynchronous serial bus system and belongs to the field buses (see the Wikipedia entry relating to this in the version of Jul. 15, 2010).
Controllers consume energy, with the result that their operation results in a battery being discharged. The CAN bus is used in a vehicle, in particular, and its battery can be discharged by the controllers.
For this reason, the controllers always deactivate themselves per se after a predetermined time. If the operation of a controller is now dependent on communication or cooperation of other controllers, it may prevent these other controllers from deactivating themselves by emitting a message for keeping these other controllers active (such a message can also be referred to as a network management message).
The message contains, in particular, at least one bit which is used to communicate a reason for keeping the controllers active.
It may now be the case that a controller operates incorrectly, for example by virtue of a corresponding software module for emitting the keep-active message not operating properly. In this case, a keep-active message may be emitted even though this is not required at all. The other controllers are then kept active and energy is permanently consumed, which eventually results in the complete emptying of the associated battery as the energy source.
A so-called “watchdog function” is known from DE 2004 026 383 B4 in connection with bus controllers.